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Tritrichomonas Foetus PCR Assay

Tritrichomonas foetus – the organism

Tritrichomonas foetus, a flagellated protozoan parasite, has been associated with diarrhoea in cats. It has been shown to infect and colonise the mucosa of the large intestine, and infected cats may develop chronic diarrhoea (increased frequency of defaecation, cow-pat to liquid faeces, which occasionally contain fresh blood/mucous). Weight loss is not a significant feature.

A USA study showed 31% of cats at a show were infected with Tritrichomonas foetus, suggesting it may be a common infection in cats. Subsequent studies from the USA as well as data from our Tritrichomonas foetus PCR assay show that any age can be infected, although diarrhoea is most common in cats under 1 year. The majority of affected cats originate from rescue shelters and colonies of pedigree cats.

The data from our Tritrichomonas foetus PCR assay shows an overall positive rate of 13% of samples submitted, but in the population of cats under one year, the detection rate rises to 40%. Pedigree cats comprise most of the positive cases with a few positive DSH’s from rescue colonies; we have detected the organism in only one DLH that originated from and resided in a domestic setting. We have detected Tritrichomonas foetus in samples from the UK, Italy and Sweden.


The PCR assay offers the most sensitive method of detecting Tritrichomonas foetus although the organism is shed intermittently. We recommend that faeces are collected over 24 hours and aliquots pooled. We prefer to receive 3-5g faeces submitted in a sterile container. Please do not use/include cat litter of any sort. Samples from up to four cats in a colony can be pooled and tested as one sample.


Clinical signs resolve in most affected cats although this can take many months. We have identified adult carriers of Tritrichomonas foetus who showed no clinical signs


Dr Jody Gookin reported that ronidazole and tinadazole may be effective against Tritrichomonas foetus infection (JVIM, 2006;20:536; Am J Vet Res, 2007; 68:1085); ronidazole appears to be more effective.

Neurological signs (twitching and seizures) have been occasionally reported in cats receiving ronidazole, which resolve on cessation of treatment. Ronidazole is not licensed for use in cats; use with caution and with informed consent.

A dose of 30mg/kg q24h has been suggested for most cats, reduced to 10mg/kg q24h for young kittens or cats with liver disease.

For further information on Tritrichomonas foetus infection in cats see the Feline Advisoy Bureau (FAB) website.

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